Apparatus for generating a hot gaseous blast



3 Sheets-Sheet 1 Oct. 19, 1965 w. M. PERRY APPARATUS FOR GENERATING A HOT GASEOUS BLAST Filed May 7, 1963 INVENTOR. W1 75PM Paeey ATTORNEY Oct. 19, 1965 w, M. PERRY 3,212,557

APPARATUS FOR GENERATING A HOT GASEOUS BLAST Filed May 7, 1963 5 Sheets-Sheet 2 --is i4 62 'Tlclib.

TIP/7449147955 Elfin 7 or 66 P147727? 0 INVENTOR. raw 12522;

ATTORNEY Oct. 19, 1965 w. M. PERRY 3,212,557

APPARATUS FOR GENERATING A HOT GASEOUS BLAST Filed May 7, 1963 5 Sheets-Sheet 3 f l my 54 5/ O f? W g/49 Q V I Jr 56E 56F 565 567.565 56F 56* 565 551C555 56E INVENTOR.

ATTORNEY 3,212,557 APPARATUS FOR GENERATING A HOT GASEOUS BLAST Walter M. Perry, Darien, Cnn., assignor to Johns-Manville Corporation, New York, N.Y., a corporation of New York Filed May 7, 1963, Ser. No. 278,647 17 Claims. (Cl. 158-99) This invention relates generally to apparatus for generating a high velocity stream of hot products of combustion. More specifically, this invention relates to a refractory tunnel burner for generating a relatively Wide and flat hot gaseous blast of high temperature and high velocity.

In the gaseous heating art there are applications which require the use of burners which develop a high temperature and high velocity generally wide flat blast of heating gases and most particularly in the local heating of work which is being continuously advanced in planar array in relation to the blast such as in the flame hardening and flame drawing or attenuating processes. Since in certain of these applications the Work or material being heated is continuously advanced, in order to obtain generally uniform heating conditions it is necessary to produce the heating gases at a rate at least as great as that at which the work is advanced. Generally, there is no time for soaking heat. Consequently, it is most desirable to use a premixed fuel to accelerate the combustion process. However, certain difficulties have been experienced in the ignition of such fuels in regard to flashback (back-fire) and to blow-off (isolation of flame from emitting port). Difliculties have also been encountered in providing a refractory-type tunnel burner having a satisfactory operational life at a low noise level.

Refractory tunnel-type burners are known in the art as means for accelerating the speed of combustion of burning gaseous mixtures. However, the use of premixed admixtures of combustible fuel and air develops high temperatures and severe service conditions which tend to rapidly deteriorate the refractory material. When the deterioration reaches a certain stage, the operating efliciency of the burner is so adversely affected that reconditioning is required. Specifically, the deterioration has resulted from spalling, slagging, or abrasion, or some combination of these. Spalling may be defined as the physical break down, deformation, or crushing of the refractory attributable to thermal, mechanical or structural causes. Slagging is the destructive action that ocurs in the refractory due to chemical reactions occurring at elevated temperatures. Abrasion is considered to be the deterioration of the refractory surface by the scouring action of solids moving in contact therewith. The solids may be carried by or formed in the combustion gases.

It is generally considered that in the most eflicient types of refractory tunnel burners the refractory has good insulating properties, high heat resistance and a rough surface texture. After the burner is lighted the refractory is heated and thereafter serves to maintain ignition. The roughness of the refractory surface causes the gases flowing adjacent thereto to be highly turbulent and to exert a catalytic effect upon and consequently accelerate combustion.

However, when such tunnel burners are operated at temperatures in the range of 2600-3450 F., the deterioration of the refractory, particularly that due to spalling, is greatly accelerated and the operational efliciency is adversely affected. When deformation disrupts the designed configuration of the tunnel discharge outlet the desired flame or burning gas pattern cannot be produced and the maximum burner efliciency cannot be attained.

United States Patent 0 The problem of refractory deterioration is particularly acute in those applications where it is desired to employ a wide and relatively flat blast of products of combustion because of the natural tendency of gaseous mixtures to burn and expand radially as they are propagated in an axial stream. This same phenomenon makes it difficult to achieve uniform distribution, velocity and temperature of the products of combustion across the width of the blast. If the distribution, velocity and temperature are not closely and uniformly maintained across the width of the blast, the work subjected to the blast will not be uniformly heated unless suflicient time is provided for the heat to soak through the work. In some continuous processes it is economically unfeasible to so extend the time during which the work is exposed to the blast.

It is an object of this invention to provide an improved refractory tunnel burner in which combustion of a premixed combustible admixture and the operational efficiency are enhanced.

It is another object of this invention to provide a refractory combustion tunnel burner having an increased operational service life and a relatively low noise level.

It is a further object of this invention to provide a burner adapted to discharge the products of combustion in a generally and relatively flat and wide stream with substantially uniform distribution, velocity, and temperature throughout all or most of the cross-sectional area of the stream.

To accomplish the stated objects, the novel burner of this invention is designed to deliver one or more primary streams of premixed fuel from 21 preferably metallic burner block for discharge into a refractory tunnel having an inlet opening of a configuration suitable for the number of primary streams employed, preferably an elongated rectangle, and an outlet opening similar in configuration to the inlet opening. Portions of the total gases discharged into the tunnel may be diverted, in the form of secondary streams, into angular contact and impingement upon the refractory adjacent to the inlet of the tunnel. These secondary streams also serve as pilots or ignition facilitating means for the primary streams during the start-up of the burner. The portion of the tunnel immediately adjacent the inlet opening, where both the secondary and primary streams impinge, or surfact catalyst zone, is preferably of low density refractory as compared to the refractory of the remainder, or main refractory zone, of the tunnel. The primary streams tend to impinge the refractory in the areas at a distance from the emitting ports corresponding to the side adjacent a ten degee angle, which is considered to be the angle of material diffusion of burning gases. The low density refractory defines a surface catalyst zone heated by the flames emanating from the secondary fuel streams, and which forms ignition means for the primary streams. The higher density refractory of the remaining and major portion of the tunnel is more resistant to spalling, at the temperatures in the range of 2600 to 3-450 F., than the comparatively low density refractories usually empoyed throughout tunnel burners. The composite refractory structure of the tunnel is a significant and important feature of this invention in that it provides a proper balance of the desired refractory properties or characteristics which unfortunately are not obtainable in a single refractory. I

The invention will be more fully understood, and further objects and advantages thereof will become apparent by reference to the following detailed description in conjunction With the accompanying drawing, in which like reference characters designate like parts, and in which:

FIG. 1 is a plan view of one form of the burner of this invention;

FIG. 2 is an elevational view of the burner of FIG. 1,

with the burner tunnel shown in cross section taken along the longitudinal center line thereof;

FIG. 3 is an enlarged front elevational view of the metal burner block of the burner shown in FIGS. 1 and 2;

FIG. 4 is a transverse cross-sectional view of the burner block taken along lines 44 of FIG. 3;

FIG. 5, on Sheet #3 of the drawings, is a transverse cross-sectional view of the burner block taken along lines 55 of FIG. 3;

FIG. 6, on Sheet #2 of the drawings, is a transverse cross-sectional view of an alternate embodiment of the burner tunnel;

FIG. 7 is a view similar to FIG. 3 but of an alternate embodiment;

FIG. 8 is a view similar to FIG. 6 but of a further modified embodiment;

FIG. 9 is a further modification of the burner tunnel; and

FIG. 10, on Sheet No. 1 of the drawings, is a crosssectional view of the burner tunnel entrance taken along line 1010 of FIG. 2.

The burner 30, as shown in FIGS. 1-3, preferably and generally comprises an elongated metal body defining a burner block 50 and a tunnel 54 defined by refractory walls 56 encased by a metal housing 52. A conduit member 58, which may generally be described as a manifold, is provided to form the transition between the cylindrical supply pipe 60 and the elongated burner block 50. The pipe 60 is suitably connected to a source of supply of an admixture of combustible fuel and air (not shown). It is preferred that the length of passage or conduit directing the admixture from the mixing station or point to the burner block 50 be at least five feet to insure that the components have ample opportunity to form a homogeneous admixture. Conduit member 58 directs the admixture fuel to the rear or exterior face 62 of burner block 50. It is to be noted that the conduit 58 makes a smooth transition from the generally round supply pipe 60 to generally rectangular burner block 50 and that the transition is to a plane coincident with the central axial plane extending through the width of the block 50. This arrangement facilitates the uniform distribution of the fuel across the lateral width of the block. It will be apparent that the supply pipe 60 may be comprised of multi-lateral uniform cross-sectional configurations other than round and for which a smooth transition is necessary to obtain a uniform distribution of fuel across the lateral pattern of the gas passage means of block 50. Accordingly, the phrase multi-lateral uniform cross-sectional configuration is intended to include those which are concentric, or generally circular, and those which are generally square, as opposed to those configurations which are elongated in one direction.

The burner block 50 is provided with a primary or first group of passages 64 extending straight therethrough, parallel to the longitudinal axis of block 51), to front face 66. The front face 66 of burner block 50 defines the discharge terminal ports of passages 64 which are preferably positioned to discharge the fuel therefrom to the inlet 55 of tunnel 54 in streams parallel to the center axis of tunnel 54. While a single row of primary passages 64 arranged in a lateral pattern across the face 66 and with their axes coincident with the central axis plane of tunnel 54 is shown in FIG. 3, the primary passages may take the form of passages 164 as shown in FIG. 7, e.g., arranged in clusters. In any event, it is preferred that the total vertical height of a passage 64 or of a cluster of passages 164 be equal to or greater than half the height of the front face 66 at the interior or discharge end of block 50. The burner block 50 is also preferably provided with a second or secondary group of passages 70, the terminal discharge ports 71 of which diverge at angle from the longitudinal axis of block 50 and are displaced from the plane 73 in which the outlets of passages 64 are preferably aligned. Preferably, the angle is in the range of 10-15 degrees. Also, preferably, there is a pair of pilot passages 70 between each pair of primary passages 64, or between each cluster of passages 164, and at each end of the pattern row of passages 64, or cluster of passages 164, for reasons hereinafter to be described. However, in some instances, the secondary passages designated as 70E and positioned outwardly of the primary passages at each end of the row may suflice. Further, it is preferred that any selected or given outlet diameter of the secondary passages 70 be less tha the given diameter of the primary passages 64. The outlet diameter of the secondary passages 70 are also sufficiently small to preclude any tendency for the combustible gases to flash-back in the passages.

Also, the axial extent of the metal block is such that the primary passages 64 therethrough are of significant axial extent in relation to the diameter thereof, preferably a length equal to at least five diameters, to quench any flame tending to travel backwardly and flash-back. Normally, flash-back occurs during restart of a burner. After the burner has been firing and is turned off for a short time, heat radiating from the refractory tunnel tends to heat the manifold sufficiently to sustain ignition within the fuel passages when the fuel is slowly turned on again. However, even under these conditions, the axial extent is sufficient to overcome flash-back. During full firing the mass flow of the fuel cools the passages sufiiciently to off-set the heat radiated from the refractory.

In order to facilitate ignition of the premixed gaseous combustible mixture, block 50 may be provided with ignition means shown to be in the form of a spark plug 72.

The burner of this invention also provides certain safety features which will be described now. The front face 66 of burner block 50 is of reduced cross section when compared to the main body 51 to minimize heat transfer from tunnel 54 through the metal of the block 50. The passing of the fuel through the relatively long passages 64 forming extended surfaces tends to maintain the block 50 relatively cool. Otherwise, if the block 50 became too hot, flash back might occur or else the admixture might be excessively preheated and consequently the velocity of the primary streams might be increased to an undesirable degree. The step formation 49 also deters the tendency for any gases to leak and burn between the block 50 and the enveloping refractory 74. End flange 76 encases the refractory 74 and is sealingly secured to body 51, as by welding 75, to prevent any leakage or explosion of gases rearwardly of the burner 30. The peripheral portion 78 of end flange 76 is also sealingly secured to back plate 80. A major portion of the length of the body 51 is exposed to the ambient air in order to minimize the surface temperature of the rear portion of the burner 30 and the likelihood of the attendant operators being burned.

The combustile gases from burner block 50 are emitted through laterally elongated inlet into tunnel 54 for burning therein and then the burning gases are discharged through discharge opening 59, preferably having a configuration similar to the inlet 55. The various sections of tunnel 54 are defined by refractory walls 56. At the entrance or inlet 55 of tunnel 54, the refractory wall portion 56A, defining a surface catalyst zone, is preferably of low density, in the general range of 45-70 lb./ft. refractory, such as the highly pure kaolin clay marketed by the Babcock-Wilcox Company and known as K-30. It has been discovered that the use of such low density refractory, in the area where the gases from the secondary ports impinge, en'hances combustion of the gases and also reduces the operational noise level, particularly whistling, of the burner. Some of the prior art high temperature and high velocity tunnel burners operate at a noise level of 110-120 decibels whereas burners of the instant invention have been operated with a noise level of -95 decibels. The remainder of the walls 56, defining a main refractory zone, is preferably of castable refractory having a density in the general range of 71-165 lb./ft.

such as the aluminum oxide-calcium aluminate compositions, marketed by the Norton Company and designated as 331 or 33HD and more preferably in the range of 100-130 lb./ft.

The present invention provides a proper balance of the desired physical properties of refractories such as thermal expansion, thermal conductivity and porosity, in a refractory tunnel. A relatively low density refractory with low thermal conductivity is provided at the entrance end of the tunnel where combustion of the gaseous fuel is initiated to increase the environmental temperature and thus enhance the combustion. To further enhance combustion, a minor portion of the combustion gases, those from the secondary ports, may be diverted for direct impingement upon the low density refractory. These diverted gases are combusted almost immediately and envelope the gases emanating from the primary ports without substantially disrupting the generally straight-through laminar flow of the primary gases. The heat emanating from the burning gases of the secondary streams and from the incandescent refractory enhances the combustion of the primary gas streams.

The higher density refractory is preferably desired for use in the major portion of the tunnel because of its higher thermal conductivity characteristic. Higher thermal conductivity permits the quick transfer of heat from the surface of the refractory exposed to the heating gases to the cooler unexposed surface to hold the temperature of the exposed surface Within the working limits of the refractory.

As illustrated in FIG. 6 the refractory 56' of the main refractory zone may be backed by a lower density refractory 56B to deter heat conduction to the casing 52. In this embodiment it is preferred that the refractory 56' have a density in the general range of 100130 lb./ft. and that the refractory 5613 have a density in the general range of 71-100 lb./ft. It is also preferred that the nose refractory 56C be of a high density castable refractory having a density in the general order of 165 lb./ft. The refractory 56D, surrounding the refractory 56A, is also preferably a castable refractory to facilitate fabrication. The refractories 56D and 74 preferably have a density in the general order of 200 lb./ft.

The main refractory zone may also be defined by intermittent or alternate sections of high and low density refractories 56E and 56F, respectively (when compared With each other), in what may be termed a zebra formation and as illustrated in FIGS. 8 and 9. Consequently, the alternate pattern provides an arrangement wherein the thermal conductivity characteristics of the various refractories may be synergistically and advantageously combined. The construction shown in FIG. 9 provides an arrangement wherein the refractories 56E and 56F are arranged in mutually opposing half-sections laterally and alternately axially. 'Ihis later arrangement deters the formation of alternate hot and relatively cool axial zones because of the diiferent propensities of the high and low density refractories to re-radiate heat to the interior of the tunnel. In other words, in the arrangement illustrated in FIG. 8, and in some temperature ranges, an axial zone defined completely by high density refractory will re-radiate more heat than a next adjacent axial zone, defined completely by low density refractory, and consequently alternate hot and relatively cool zones may be generated. Alternate sections of different types of refractory may also be advantageously employed to synergistically compensate for their different volumetric tendencies when subjected to heat. Some refractories have a tendency to expand while others tend to contract. Consequently, if alternate sections of refractories which contract and those which expand are employed, spalling due to mechanical causes may be deterred. While the features relating to the selection of refractories of different densities and their location in a burner tunnel have been disclosed herein in connection with a relatively flat tunnel,

it will be apparent that the concepts may also be applied in burner tunnels of other cross-sectional configurations. However, the features are particularly adaptable for use in burners having relatively elongated tunnels with elongated gas inlet openings or discharge openings, in which case the problem of maintaining uniform distribution, velocity, and temperature is very acute. The elongated pattern of the primary port(s) and the secondary ports facilitates the achievement of uniform distribution, velocity, and temperature of the gases across the cross-sectional area of the inlet opening of the tunnel, the combination of the selected refractories and the divergent secondary ports serves to facilitate ignition of the gases and to maintain the above uniform conditions. The generally uniform rectangular cross-sectional configuration of the tunnel throughout its axial extent, as opposed to a converging tunnel, is believed to further facilitate the uniform distribution and velocity of the burning gases across a rectangular discharge port. Velocities uniform within 1-2% have been attained across the width of burners that have been built according to this invention, when operated to produce blasts in the range of 800-1000 ft./sec.

While the invention has been described in rather full detail, it will be understood that these details need not be strictly adhered to but that various changes and modifications may suggest themselves to one skilled in the art, all falling within the scope of the invention as defined by the subjoined claims.

What I claim:

1. Burner apparatus, comprising:

(a) a refractory tunnel having a rectangular and substantially constant cross-sectional configuration throughout its axial length, and wherein the refractory defining the inlet opening of said tunnel is of relatively low density, in the range of 45-70 pounds per cubic foot;

(b) a metallic burner block defining a primary passage for conducting a homogenous admixture of combustible fuel and air, and being arranged to discharge said admixture in a stream substantially parallel to the center axis of said tunnel;

(c) and means for supplying said admixture to said burner block.

2. The apparatus as described in claim 1, wherein: said tunnel comprises a main refractory zone and a surface catalyst refractory zone, said surface catalyst zone being adjacent the inlet opening of said tunnel, and wherein the refractory of said catalyst zone is of relatively low density, in the range of 45 to lb./ft. and the refractory of the main zone is of a density in the range of 71-165 lb./ft.

3. Burner apparatus, comprising:

(a) a refractory tunnel of rectangular and substantially constant cross-sectional configuration t roughout its axial length and having an inlet opening and a discharge opening,

-(b) a metallic burner block defining a plurality of passages for conducting an admixture of combustible fuel and air, said block having a front face defining the discharge portions of said passages and being positioned to discharge said admixture from said passages to the inlet opening of said tunnel,

(c) at least one of said passages defining a primary terminal discharge port of a given cross-sectional area and being arranged to discharge the admixture therefrom in a stream substantially parallel to the center axis of said tunnel,

(d) at least one other of said passages defining a secondary terminal discharge port having a cross-sectional area smaller than said given cross-sectional area of said primary port, said secondary port being arranged to discharge the admixture therefrom in a stream inclined toward the refractory defining said tunnel for impingement upon said refractory.

4. Burner apparatus, comprising:

(a) a refractory tunnel having a laterally elongated inlet opening and a laterally elongated discharge opening, said discharge opening corresponding to said inlet opening in configuration and in cross-sectional area; and

(b) a metallic burner block defining a plurality of passages for conducting an admixture of combustible fuel and air, said block having a front face defining the discharge portions of said passages and being positioned to discharge said admixture from said passages to the inlet of said tunnel,

(c) a first group of said passages having terminal discharge primary ports of a given diameter, said primary ports being arranged in a lateral pattern across the front face of said body and to discharge the admixture therefrom in streams parallel to the center axis of said tunnel, and

(d) a second group of said passages having terminal discharge secondary ports of diameter less than said given diameter of said first group of passages, said secondary ports being arranged to discharge the admixture therefrom in streams inclined toward the refractory defining said tunnel for impingement upon said refractory.

*5. The apparatus as described in claim 4, wherein second group of passages are arranged in vertical pairs, and there being at least one pair at each end of the lateral pattern of said first group of passages.

6. The apparatus as described in claim 4, wherein said first group of passages are aligned in a common horizontal plane.

7. The apparatus as described in claim 6, wherein at least a first portion of said passages of said second group terminates at said face along a plane displaced from said common plane.

8. The apparatus as described in claim 7, wherein at least a second portion of said passages of said second group terminates at said face along a plane displaced from said common plane and from the plane of said first portion of passages of said second group.

'9. The apparatus as described in claim 4. wherein: said discharge opening is of a height at least as great as the height of said inlet opening.

10. Burner apparatus, comprising:

(a) a refractory tunnel of rectangular and substantially constant cross-sectional configuration and having an elongated inlet opening and a discharge opening;

(b) a burner block adjacent to said inlet opening and defining a plurality of passages,

(c) a first group of said passages being arranged in a lateral pattern across said inlet, the dimension of said pattern transverse to the elongated extent of said inlet opening being equal to at least one-half the dimension of the transverse extent of said inlet opening,

I(d) a second group of said passages, each having a diameter less than the diameter of any of said passages of said first group, being positioned with their discharge ends closer to the refractory of said tunnel than the central axis of any of said passages of said first group; and

(e) a manifold at the exterior face of said block providing a combustible homogeneous admixture to said passages.

11. The apparatus as described in claim 10, wherein said second group includes a pair of passages intermediate each pair of the passages of said first group.

12. Burner apparatus, comprising:

a) a refractory tunnel defining an inlet opening and a discharge opening;

(b) said discharge opening being substantially rectangular and having a height at least as great as the height of said inlet opening;

' (c) a metal body defining a plurality of longitudinal passages,

(d) said body having a front face positioned in axial alignment with and contiguous to said inlet opening,

(e) a first group of said passages being arranged in a pattern extending lengthwise of said face,

!(f) a second group of said passages, each passage in said second group having a diameter smaller than the diameter of the passages of said first group,

(g) the passages of said group being arranged in vertical pairs, there being a pair at each end of the pattern of passages of said first group,

(h) said second group of said passages having a discharge end portion having a longitudinal axis diverging from the longitudinal axis of said combustion chamber and being adapted to direct gases for impingement upon the refractory of said combustion chamber.

13. Burner apparatus, comprising:

(a) a refractory tunnel having a laterally elongated inlet opening and a laterally elongated discharge opening;

(b) said discharge opening being of a height at least as great as the height of said inlet opening;

(0) a burner block defining a plurality of passages for conducting an admixture of combustible fuel and air, said block having a front face defining the discharge portions of said passages and being positioned to discharge said admixture from said passages to the inlet of said chamber,

(d) a first group of said passages having terminal discharge ports of a given diameter, said ports being arranged in a lateral pattern across the front face of said body and to discharge the admixture therefrom in streams parallel to the center axis of said I tunnel,

(e) a second group of said passages having terminal dis-charge ports of diameter less than said given diameter of said first group of passages, said ports being arranged to discharge the admixture therefrom in streams inclined toward the refractory defining said tunnel for impingement upon said refractory,

(f) said burner block having a front terminal portion and a main body portion, said front terminal portion being reduced in cross-section as compared to said main body of said block,

(g) said reduced front terminal portion being enveloped by insulating refractory;

(h) an end flange encasing said front terminal portion and the enveloping refractory but leaving a major portion of the length of said body exposed to the ambient ah,

(i) said end flange being sealingly secured to said body;

(j) a metallic housing en-casing the refractory of said tunnel; and

(k) ignition means in communication with at least one igniting the admixture passing therethrough. of said passages of said first group for initially 14. A tunnel burner, comprising:

(a) a refractory tunnel defining an inlet opening and a discharge opening, and a refractory surface catalyst zone and a refractory main zone;

(b) said surface catalyst zone being adjacent to said inlet opening and comp-rising refractory of relatively low density, in the range of 45-70 lb./ft. and

(c) said main zone comprising refractory of relatively higher density in the range of 71l65 lb./ft.

15. A tunnel burner, comprising:

(a) a refractory tunnel defining an inlet opening, a

discharge opening, and a surface catalyst zone adjacent to said inlet opening,

(b) said zone comprising refractory of relatively low density in the range of 45-70 lb./ft. and

(c) the remainder of said tunnel being comprised of alternate axial sections of said refractory of low density and of refractory having a density in the range of 71-165 lb./ft.

16. A refractory tunnel comprising sections of relatively high and low density refractories arranged alternately axially of the tunnel and in mutually facing relation normal to the axis of the tunnel, there being at least two sections of relatively high density refractory and at least two sections of relatively low density refractory, said high density refractories having a density in the range of 71-160 lb./ft. and said low density refractories having a density in the range of 45-70 lb./ft. said tunnel comprising a surface catalyst zone at the entrance thereof defined by low density refractory.

17. Burner apparatus, comprising:

(a) a refractory tunnel having a laterally elongated inlet opening and a laterally elongated discharge opening;

(b) a burner block adjacent to said inlet opening and defining gas passage means extending generally axially therethrough and arranged in a lateral pattern cor-responding generally to the lateral extent of said inlet opening,

(c) at least a portion of said passage means being arranged to discharge fuel in a direction inclined toward and for impingement upon said refractory; and

(d) a manifold connected to said block,

(c) said manifold forming a smooth transition from a conduit having multi-lateral uniform dimensions to an enlongated pattern corresponding to the lateral pattern of said gas passage means of said burner block, and

(f) at least a terminal portion of said manifold adjacent to said block having a central axis coextensive with the central axis of said burner block.

References Cited by the Examiner UNITED STATES PATENTS 1,138,482 5/15 Ionides 1587 1,227,277 5/17 Land 158-99 1,253,342 1/18 Bone et al. 15899 1,308,364 7/19 Lucke 15899 1,807,977 6/31 Frank 158-104 2,070,859 2/37 Don Howe 1587 X 2,194,208 3/40 Moran 15899 2,402,045 6/46 Hess 15899 2,888,980 6/59 Williams et al. 158116 FOREIGN PATENTS 716,388 10/31 France.

JAMES W. WESTHAVER, Primary Examiner.

FREDERICK L. MATTESON, JR., Examiner. 

1. BURNER APPARATUS, COMPRISING: (A) A REFRACTORY TUNNEL HAVING A RECTANGULAR AND SUBSTANTIALLY CONSTANT CROSS-SECTIONAL CONFIGURATION THROUGHOUT ITS AXIAL LENGTH, AND WHEREIN THE REFRACTORY DEFINING THE INLET OPENING OF SAID TUNNEL IS OF RELATIVELY LOW DENSITY, IN THE RANGE OF 45-70 POUNDS PER CUBIC FOOT; (B) A METALLIC BURNER BLOCK DEFINING A PRIMARY PASSAGE FOR CONDUCTING A HOMOGENOUS ADMIXTURE OF COMBUSTIBLE FUEL AND AIR, AND BEING ARRANGED TO DISCHARGE SAID ADMIXTURE IN A STREAM SUBSTANTIALLY PARALLEL TO THE CENTER AXIS OF SAID TUNNEL; (C) AND MEANS FOR SUPPLYING SAID ADMIXTURE TO SAID BURNER BLOCK. 